#11804: delta_qexp() fails in large characteristic
--------------------------------+-------------------------------------------
   Reporter:  jdemeyer          |          Owner:  AlexGhitza                   
                                           
       Type:  defect            |         Status:  new                          
                                           
   Priority:  major             |      Milestone:  sage-4.7.2                   
                                           
  Component:  basic arithmetic  |       Keywords:  FLINT NTL polynomial 
_mul_short _mul_trunc delta_qexp _delta_poly_modulo
Work_issues:                    |       Upstream:  N/A                          
                                           
   Reviewer:                    |         Author:                               
                                           
     Merged:                    |   Dependencies:                               
                                           
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 Sage fails to compute the q-expansion of the Delta modular form in large
 (>= machine word) characteristic:
 {{{
 sage: R = IntegerModRing(5^100)
 sage: delta_qexp(200, 'q', R)
 Exception OverflowError: 'long int too large to convert' in  ignored
 ---------------------------------------------------------------------------
 OverflowError                             Traceback (most recent call
 last)

 /home/jdemeyer/<ipython console> in <module>()

 /usr/local/src/sage-4.7.1/local/lib/python2.6/site-
 packages/sage/modular/modform/vm_basis.pyc in delta_qexp(prec, var, K)
     389     ch = K.characteristic()
     390     if ch > 0 and prec > 150:
 --> 391         return R(_delta_poly_modulo(ch, prec), prec, check=False)
     392     else:
     393         # compute over ZZ and coerce

 /usr/local/src/sage-4.7.1/local/lib/python2.6/site-
 packages/sage/modular/modform/vm_basis.pyc in _delta_poly_modulo(N, prec)
     307
     308     P = PolynomialRing(Integers(N), 'q')
 --> 309     f = Polynomial_zmod_flint(P, x=v, check=False)
     310     t = verbose('made series')
     311     # fast way of computing f*f truncated at prec

 /usr/local/src/sage-4.7.1/local/lib/python2.6/site-
 packages/sage/rings/polynomial/polynomial_zmod_flint.so in
 sage.rings.polynomial.polynomial_zmod_flint.Polynomial_zmod_flint.__init__
 (sage/rings/polynomial/polynomial_zmod_flint.c:11069)()

 /usr/local/src/sage-4.7.1/local/lib/python2.6/site-
 packages/sage/rings/polynomial/polynomial_zmod_flint.so in
 sage.rings.polynomial.polynomial_zmod_flint.Polynomial_template.__init__
 (sage/rings/polynomial/polynomial_zmod_flint.c:5301)()

 /usr/local/src/sage-4.7.1/local/lib/python2.6/site-
 packages/sage/rings/polynomial/polynomial_zmod_flint.so in
 sage.rings.polynomial.polynomial_zmod_flint.get_cparent
 (sage/rings/polynomial/polynomial_zmod_flint.c:2599)()

 OverflowError: long int too large to convert
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11804>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
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